Q. How to Change Default Drive in dos?

To modify a default drive type the new drive letter followed by colon (:) and then press Enter.  For example, if the default drive is A and you type C: and press Enter, DOS selects drive C: as the default drive.  DOS verify this by changing the prompt to C:\> or a similar message.  If you enter a drive letter that does not exists in your PC, DOS displays a message "Invalid Drive Specification".

When you choose a floppy drive as the default drive, make sure that there is a diskette is inserted in that drive.  Otherwise, DOS gives the following message:

            "Not ready reading drive A

            Abort, Retrieve, Fail ?

If you get this message, insert a diskette in the floppy drive and then press "r" to Retrieve.